We have developed a unique system for studying the differentiation of rat lens epithelial cells in tissue culture. We investigated the steps of cortical cataract formation in intact rat lenses in tissue culture. We found many similarities in processes occurring (1) in cataractogenesis in intact lenses and (2) in tissue culture monolayers grown under similar conditions. Specifically, cytochalasin D, an inhibitor which acts on actin microfilaments, causes cells in vitro to react and form globules, and causes cortical lens fiber cells to undergo cataractous globular degeneration, with associated lens opacity and loss of acuity. High levels of glucose, which can cause cataracts in intact lenses; inhibit growth of cells of the lens cell line RLE-R. We plan to further explore the similarities between the processes occurring in intact lenses and in tissue culture monolayers to ascertain whether the process of cataractogenesis can be modelled in tissue culture. We plan to continue our investigations of the change in actin organization, which appears to be a prerequisite for the expression of the differentiation-specific protein, gamma-crystallin: (1) in primary cultures of lens epithelial cells and (2) cultures of our cell line RLE-R induced to produce gamma-crystallins.